Luke Massey / Close-up of a Wild boar (Sus scrofa) approaching a remote camera and knocking it over, Forest of Dean, Gloucestershire, England, UK, May.

Frederique Olivier / Southern rockhopper penguin (Eudyptes chrysocome) at nest in breeding colony, stretching and knocking chick over, New Island, Falkland Islands.

Markus Varesvuo / Puffins (Fratercula arctica) 'bill-knocking' in a display of courtship behaviour, Norway, Scandinavia, April.

Markus Varesvuo / Puffins (Fratercula arctica) 'bill-knocking' in a display of courtship behaviour, Norway, Scandinavia, April.

Alan Williams / Sand Martin (Riparia riparia) one bird knocking other bird off cliff during rivalry for nesting place, Wirral Merseyside UK June

Alan Williams / Sand martin (Riparia riparia) right hand bird knocking other bird off cliff during rivalry for nesting place, Wirral Merseyside UK June

Charlie Summers / Pair of Franklin's Gulls (Leucophaeus pipixcan) beak knocking, Guls Shores, Alabama, USA, April

Pete Oxford / Brown Capuchin (Cebus apella) pair sitting on anvil used to crack open Piassava Palm (Attalea funifera) nut, monkey on left knocking nuts together to test for freshness, Cerrado habitat, Piaui State,...

Anup Shah / Adult Chimpanzee knocking insect off tree trunk {Pan troglodytes schweinfurtheii} Kasekela community, Gombe NP, Tanzania. 2002

Anup Shah / Adult Chimpanzee, possibly knocking insect off tree trunk {Pan troglodytes schweinfurtheii} Kasekela community, Gombe NP, Tanzania. 2002

Rick Tomlinson / Charles St. Clare-Brown, the owner of ICAP "Maximus", racing during Skandia Cowes Week, Solent, UK, 2006. ^^^ He grabbed the opportunity to blast around the Isle of Wight in an astonishing 3 hours, 20...

Rick Tomlinson / Charles St. Clare-Brown's ICAP "Maximus" during Skandia Cowes Week, Solent, UK, August 3, 2006. ^^^ "Maximus" grabbed the opportunity to blast around the Isle of Wight in an astonishing 3 hours, 20 mi...